The United States pressed Macedonia on Thursday to investigate possible evidence of abuse of power, brought to light by leaked wiretaps that allegedly demonstrated government control over judges, journalists and elections.

The U.S. move stepped up diplomatic pressure on the conservative government of Nikola Gruevski to address the content of wiretaps released by Zoran Zaev, leader of the opposition Social Democrats. He said he got them from an intelligence service whistleblower.

Police have charged Zaev with conspiring with a foreign spy service to topple the government.

Hoyt Yee, U.S. deputy assistant secretary of state for European and Eurasian affairs, who was visiting Macedonia, said authorities were obliged to examine the content of the tapes, which purportedly include conversations involving Gruevski, cabinet ministers and security chiefs, as well as journalists, judges and religious figures.

The government has not explicitly confirmed or denied the identity of the voices on the tapes, but it has disputed their reliability as evidence of wrongdoing. It also denies being behind the wiretaps.

Yee told reporters after meeting Gruevski that while it was important to address the question of responsibility for the wiretaps and their release, "there are also questions raised about the possibility of abuse of government power, which also need to be addressed.''

Yee cited information about "possible official corruption, possible inappropriate government influence over the media, over the judiciary, possible electoral abuse and other abuses of power.''

Gruevski did not address reporters after the meeting.

Political opponents of the government said the tapes exposed an autocratic shift in Macedonia under Gruevski, who has been in power since mid-2006.

The West's ability to encourage reform and the strengthening of democracy, a policy pursued across the Western Balkans, has been stunted in Macedonia by the fact that its bids to join the European Union and NATO have been blocked for years by a dispute with neighboring Greece over Macedonia's name.

Three members of the European Parliament are trying to help mediate a solution to the crisis, but both the government and opposition say they want a more high-profile intervention.

Diplomats fear political instability may harm Macedonia's fragile interethnic peace, barely 15 years after it narrowly avoided civil war during fighting between government forces and ethnic Albanian guerrillas.